But the origin of this idiom is not in a boxing ring. It dates back to 1696, when John Hatfield, a guard at Windsor Castle was accused of falling asleep at his post. If found guilty, he would have been executed. In his defence, he claimed that he heard the bells at St. Paul's Cathedral ring 13 times at midnight. This appeared ludicrous, as the bells are only supposed to ring 12 times. But upon asking the townfolk, it was found that the bells did indeed ring 13 times. John was acquitted. He was 'saved by the bell'.